Transmit diversity architecture with optimized power consumption and area for umts &amp; lte systems

ABSTRACT

A method and apparatus for providing total power from one transmit path. The method provides the steps of: selecting a transmit path and closing a first switch, located after a digital to analog converter. A second switch between the two transmit paths is then closed in order to provide for the use of at least one low-pass filter in each transmit path. The signal is then processed through the at least one low pass filter in each transmit path. The signal is then processed through at least one mixer in each transmit path. After the mixer, the signal is then processed through at least one driver amplifier in each transmit path, and one-half of the total power is allocated to each of two transmission paths. A third switch is then closed after the at least one power amplifier in each transmit path to force the half-power from one transmit path into one output.

BACKGROUND

1. Field

The present disclosure relates generally to communication systems, andmore particularly, to a transmit diversity architecture with optimizedpower consumption and an area for Universal Mobile Telecommunications(UMTS) and Long Term Evolution (LTE) systems.

2. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunications with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA), 3GPP Long Term Evolution (LTE) systems,and orthogonal frequency division multiple access (OFDMA) systems, andUniversal Mobile Telecommunications (UMTS) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-in-single-out, multiple-in-single-out ora multiple-in-multiple-out (MIMO) system.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, where N_(S) _(—) ≧min {N_(T), N_(R)}. Eachof the N_(S) independent channels corresponds to a dimension. The MIMOsystem can provide improved performance (e.g., higher throughput and/orgreater reliability) if the additional dimensionalities created by themultiple transmit and receive antennas are utilized. When multipletransmit antennas are used, the system can also be described as havingtransmit diversity.

A MIMO system may support time division duplex (TDD) and/or frequencydivision duplex (FDD) systems. In a TDD system, the forward and reverselink transmissions can be on the same frequency region so that thereciprocity principle allows the estimation of the forward link channelfrom the reverse link channel. This enables the base station to extracttransmit beamforming gain on the forward link when the multiple antennasare available at the base station. In an FDD system, forward and reverselink transmissions are on different frequency regions.

Modern cellular phones support multiple carriers and modes of operation.Increasingly, mobile devices are using MIMO systems to provide improvedwireless communication performance. While mobile devices often utilizethe latest advances in technology, there remains a need to providelegacy services. Frequently, a mobile device must be capable of transmitdiversity while still operating in a legacy mode when necessary.Providing such capabilities often requires an increase in silicon areato provide the added features and modes of operation.

In the past, multiple transmit chains for MIMO or transmit diversity forcellular communications may have been implemented using multipletransmit chips. However, this is an inefficient use of silicon area andpower and requires duplicate synthesizers for the two transmit chips.Duplicate transmit chains could have been implemented on the same chip,thus saving a synthesizer, but this causes the chip area to growdramatically, which makes the chip unsuitable for products which onlysupport the legacy mode, and causes high power consumption in the MIMOor transmitter diversity mode. There is a need in the art for a systemarchitecture that provides for transmit diversity and optimized powerconsumption and is also suitable for use with UMTS and LTE systems. Inaddition, there is a need in the art for a space saving on the chip, anda need for a reduced size transmit chain.

SUMMARY

Embodiments disclosed herein provide system architectures with optimizedpower consumption and area for transmit diversity for use in UMTS andLTE systems. An apparatus for transmit diversity in a multiple inputmultiple output (MIMO) network is provided. The apparatus provides twoinput digital to analog converters, each accepting a data input; twotransmit paths, each path comprising at least one low pass filter, atleast one mixer, and at least one pre-power amplifier or driveramplifier; at least one switch connecting the two transmit paths beforeboth digital analog converters or following both digital to analogconverters and before an input to that at least one low pass filter orafter the at least one low pass filter and before the at least one mixeror after the at least one mixer; and a second switch connecting the twotransmit paths after a mixer and pre-power amplifier. The pre-poweramplifier may also be called a driver amplifier. The switches provide amechanism to deliver total power at a first transmit data streamtransmission point.

A further embodiment provides a method for providing total power fromtwo transmit paths. The method provides the steps of: selecting atransmit path input and selecting one of the digital to analogconverters. A first switch between the two transmit paths is then closedin order to provide for the use of at least one low-pass filter in eachtransmit path. The signal is then processed through the at least one lowpass filter in each transmit path. The signal is then processed throughat least one mixer in each transmit path. After the mixer, the signal isthen processed through at least one pre-power amplifier or poweramplifier in each transmit path, and one-half of the total power isallocated to each of two transmission paths. A second switch is thenclosed after the at least one pre-power amplifier or driver amplifier ineach transmit path to force the half-power from each pre-power amplifieror driver amplifier into one output.

A still further embodiment provides an apparatus for providing totalpower from two transmit paths. The apparatus provides means for closinga first switch between the two transmit paths to provide for the use ofat least one low pass filter in each transmit path; means for processingthe signal through the at least one mixer in each transmit path; meansfor processing the signal through the at least one pre power amplifieror driver amplifiers in each transmit path, wherein half of the totalpower is allocated to each transmission path; and means for closing asecond switch after the at least one pre-power amplifier or driveramplifier in each transmit path to force the half-power from eachtransmit path into one output.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a multiple access wireless communication system, inaccordance with certain embodiments of the disclosure.

FIG. 2 illustrates a block diagram of a communication system inaccordance with certain embodiments of the disclosure.

FIG. 3 illustrates a MIMO system architecture typically used in awireless communication system.

FIG. 4 illustrates a transmitter architecture that can be configured foreither MIMO operation or legacy operation in accordance with anembodiment of the disclosure.

FIG. 5 illustrates an architecture of a transmit diversity architecturewhen configured for legacy operation in accordance with an embodiment ofthe disclosure.

FIG. 6 illustrates an architecture of a transmit diversity architecturewhen configured for MIMO or transmit diversity operation in accordancewith an embodiment of the disclosure.

FIG. 7 illustrates an architecture of a transmit diversity architecturein accordance with an embodiment of the disclosure.

FIG. 8 illustrates a second architecture of a transmit diversityarchitecture in accordance with an embodiment of the disclosure.

FIG. 9 illustrates a third architecture of a transmit diversityarchitecture in accordance with an embodiment of the disclosure.

FIG. 10 illustrates a fourth architecture of a transmit diversityarchitecture in accordance with an embodiment of the disclosure.

FIG. 11 is a flow diagram of a method of communicating over a transmitdiversity architecture in accordance with an embodiment of thedisclosure.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that such aspect(s) maybe practiced without these specific details.

As used in this application, the terms “component,” “module,” “system”and the like are intended to include a computer-related entity, such as,but not limited to hardware, firmware, a combination of hardware andsoftware, software, or software in execution. For example, a componentmay be, but is not limited to being, a process running on a processor, aprocessor, an object, an executable, a thread of execution, a programand/or a computer. By way of illustration, both an application runningon a computing device and the computing device can be a component. Oneor more components can reside within a process and/or thread ofexecution and a component may be localized on one computer and/ordistributed between two or more computers. In addition, these componentscan execute from various computer readable media having various datastructures stored thereon. The components may communicate by way oflocal and/or remote processes such as in accordance with a signal havingone or more data packets, such as data from one component interactingwith another component in a local system, distributed system, and/oracross a network such as the Internet with other systems by way of thesignal.

Furthermore, various aspects are described herein in connection with aterminal, which can be a wired terminal or a wireless terminal. Aterminal can also be called a system, device, subscriber unit,subscriber station, mobile station, mobile, mobile device, remotestation, remote terminal, access terminal, user terminal, communicationdevice, user agent, user device, or user equipment (UE). A wirelessterminal may be a cellular telephone, a satellite phone, a cordlesstelephone, a Session Initiation Protocol (SIP) phone, a wireless localloop (WLL) station, a personal digital assistant (PDA), a handhelddevice having wireless connection capability, a computing device, orother processing devices connected to a wireless modem. Moreover,various aspects are described herein in connection with a base station.A base station may be utilized for communicating with wirelessterminal(s) and may also be referred to as an access point, a Node B, orsome other terminology.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase “X employs A or B” is intended to mean anyof the natural inclusive permutations. That is, the phrase “X employs Aor B” is satisfied by any of the following instances: X employs A; Xemploys B; or X employs both A and B. In addition, the articles “a” and“an” as used in this application and the appended claims shouldgenerally be construed to mean “one or more” unless specified otherwiseor clear from the context to be directed to a singular form.

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), CDMA2000, etc. UTRA includes Wideband CDMA (W-CDMA).CDMA2000 covers IS-2000, IS-95 and technology such as Global System forMobile Communication (GSM).

An OFDMA network may implement a radio technology such as Evolved UTRA(E-UTRA), the Institute of Electrical and Electronics Engineers (IEEE)802.11, IEEE 802.16, IEEE 802.20, Flash-OFDAM®, etc. UTRA, E-UTRA, andGSM are part of Universal Mobile Telecommunication System (UMTS). LongTerm Evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA,E-UTRA, GSM, UMTS, and LTE are described in documents from anorganization named “3^(rd) Generation Partnership Project” (3GPP).CDMA2000 is described in documents from an organization named “3^(rd)Generation Partnership Project 2” (3GPP2). These various radiotechnologies and standards are known in the art. For clarity, certainaspects of the techniques are described below for LTE, and LTEterminology is used in much of the description below. It should be notedthat the LTE terminology is used by way of illustration and the scope ofthe disclosure is not limited to LTE. Rather, the techniques describedherein may be utilized in various application involving wirelesstransmissions, such as personal area networks (PANs), body area networks(BANs), location, Bluetooth, GPS, UWB, RFID, and the like. Further, thetechniques may also be utilized in wired systems, such as cable modems,fiber-based systems, and the like.

Single carrier frequency division multiple access (SC-FDMA), whichutilizes single carrier modulation and frequency domain equalization hassimilar performance and essentially the same overall complexity as thoseof an OFDMA system. SC-FDMA signal may have lower peak-to-average powerration (PAPR) because of its inherent single carrier structure. SC-FDMAmay be used in the uplink communications where the lower PAPR greatlybenefits the mobile terminal in terms of transmit power efficiency.

FIG. 1 illustrates a multiple access wireless communication system 100according to one aspect. An access point 102 (AP) includes multipleantenna groups, one including 104 and 106, another including 108 and110, and an additional one including 112 and 114. In FIG. 1, only twoantennas are shown for each antenna group, however, more or fewerantennas may be utilized for each antenna group. Access terminal 116(AT) is in communication with antennas 112 and 114, where antennas 112and 114 transmit information to access terminal 116 over downlink orforward link 118 and receive information from access terminal 116 overuplink or reverse link 120. Access terminal 122 is in communication withantennas 106 and 108, where antennas 106 and 108 transmit information toaccess terminal 122 over downlink or forward link 124 and receiveinformation from access terminal 122 over uplink or reverse link 126. Ina Frequency Division Duplex (FDD) system, communication links 118, 120,124, and 126 may use a different frequency for communication. Forexample, downlink or forward link 118 may use a different frequency thanthat used by uplink or reverse link 120.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access point. In anaspect, antenna groups each are designed to communicate to accessterminals in a sector of the areas covered by access point 102.

In communication over downlinks or forward links 118 and 124, thetransmitting antennas of access point may utilize beamforming in orderto improve the signal-to-noise ratio (SNR) of downlinks or forward linksfor the different access terminals 116 and 122. Also, an access pointusing beamforming to transmit to access terminals scattered randomlythrough its coverage causes less interference to access terminals inneighboring cells than an access point transmitting through a singleantenna to all its access terminals.

An access point may be a fixed station used for communicating with theterminals and may also be referred to as a Node B, an evolved Node B(eNB), or some other terminology. An access terminal may also be calleda mobile station, user equipment (UE), a wireless communication device,terminal, or some other terminology.

FIG. 2 is a block diagram of an aspect of a transmitter system 210 and areceiver system 250 in a MIMO system 200. At the transmitter system 210,traffic data for a number of data streams is provided from a data source212 to a transmit (TX) data processor 214. An embodiment of thedisclosure is also applicable to a wireline (wired) equivalent of thesystem shown in FIG. 2.

In an aspect, each data stream is transmitted over a respective transmitantenna. TX data processor 214 formats, codes, and interleaves thetraffic data for each data stream based on a particular coding schemeselected for that data stream to provided coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (e.g., symbol mapped) basedon a particular based on a particular modulation scheme (e.g., a BinaryPhase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), M-PSKin which M may be a power of two, or M-QAM, (Quadrature AmplitudeModulation)) selected for that data stream to provide modulationsymbols. The data rate, coding, and modulation for each data stream maybe determined by instructions performed by processor 230 that may becoupled with a memory 232.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain aspects TX MIMO processor 220 applies beamforming weights to thesymbols of the data streams and to the antenna from which the symbol isbeing transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby the N_(R) antennas 252 a through 252 r and the received signal fromeach antenna 252 is provided to a respective receiver (RCVR) 254 athrough 254 r. each receiver 254 conditions (e.g., filters, amplifies,and downconverts) a respective received signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX processor 260 is complementary to that performed byTX MIMO processor 220 and TX data processor 214 at transmitter system210.

Processor 270, coupled to memory 272, formulates a reverse link message.The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams for ma datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240 and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250.

The embodiments described herein provide RF MIMO or transmit diversityand legacy mode operation with minimal increases in area and currentconsumption. Transmit diversity may encompass actual transmit diversityas well as uplink multiple input-multiple output systems (UL MIMO). Theembodiments described herein lock two transmit frequencies to the samelocal oscillator (LO), which is critical for MIMO and transmit diversityperformance. The architecture embodiments described herein apply to ULMIMO, UMTS, and LTE systems.

Generally, a wireless multiple-access communication system maysimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-in-single-out, multiple-in-single-out,or a MIMO system.

A MIMO systems employs multiple (N_(T)) transmit antennas and multipleN_(R) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, where N_(S)≧min {N_(T), N_(R)}. Each of theN_(S) independent channels corresponds to a dimension. The MIMO systemcan provide improved performance, (e.g., higher throughput and/orgreater reliability) if the additional dimensionalities created by themultiple transmit and receive antennas are utilized.

A MIMO system may support time division duplex (TDD) and/or frequencydivision duplex (FDD) systems. In a TDD system, the forward and reverselink transmissions should be on the same frequency region so that thereciprocity principle allows the estimation of the forward link channelfrom the reverse link channel. This enables the base station to extracttransmit beamforming gain on the forward link when the multiple antennasare available at the base station. In an FDD system, forward and reverselink transmissions are in different frequency regions.

FIG. 3 provides an overview of the architecture of a typical MIMOsystem. The system, 300 includes the elements discussed below. Channels302A-E are input to respective spreading devices 304A-E. Channel 302A isthe dedicated physical control channel (DPCCH) 302B is the dedicatedphysical control channel (DPDCH), 302C is the high speed dedicatedphysical control channel (HS-DPCCH), 302D is the enhanced dedicatedphysical data channel (E-DPCCH) 302E is the synchronization enhanceddedicated physical control channel (S-E-DPCCH). In a similar fashion,channels 308A-D are input to a second spreading device 310. Channel 308Ais the enhanced dedicated physical data channel number 1, 308B is theenhanced dedicated physical data channel number 2, 308C is the enhanceddedicated physical data channel number 3, and 308D is the enhanceddedicated physical data channel number 4.

Channel 312, the synchronized dedicated physical control channel(S-DPCCH) in input to spreading device 316. Similarly, channels 314A-Dare input to spreading device 318. Channel 314A is the synchronizeddedicated physical data channel number 1, channel 314B is thesynchronized dedicated physical data channel number 2, channel 314C isthe synchronized dedicated physical data channel number 3, and 314D isthe synchronized dedicated physical data channel number 4.

The summer device sums the inputs from the channels that are sent to itfor processing. Each summer, 316 and 320 outputs results to a mixer.Summer 306 outputs results to mixer 322, while summer 320 outputsresults to mixer 332. Each mixer takes the I+jQ products of the summerand mixes with the S_(dpch,n) input to form an output product. Thisoutput product is then input to another two mixers, 324A and B in thecase of mixer 322, and 334A and B in the case of mixer 332. In mixer 324A weights w1 are applied and in mixer 324B weights w2 are applied. Inmixer 334A weights w3 are applied and in mixer 334B weights w4 areapplied. The products from mixer 324A are sent to summer 326. Theproducts from mixer 324B are sent to summer 336. The products from 334Aare sent to summer 326 and the products from 334B are sent to summer336. As a result, summers 326 and 336 each receive an input from bothmixers 322 and 332. Summers 326 and 336 provide inputs to the modulationfunctions 328 and 338. The modulation functions in turn deliver theirrespective outputs to antennas 330 and 340 for transmission.

The architecture of the embodiments proposed for MIMO systems uses twotransmit chains. The baseband circuits may either transmit the samesignal on both chains, or may transmit two different signals, one oneach transmit chain. The goal is to maintain legacy device operation andto provide optimal performance. In the embodiments, there are twodigital to analog converters (DAC), two data streams and one phase lockloop (PLL) and one or two local oscillator dividers. If two dividers areused, coordination between the dividers is needed when in legacy mode sothat I and Q outputs of both dividers are in phase with each other. Twoupconverters and two local oscillator buffers may also be used.

FIG. 4 illustrates a transmitter architecture that can be configured foreither MIMO operation or legacy operation. In FIG. 4, in the system 400,two data inputs DATA1 and DATA2 can be provided to two digital to analogconverters (DAC) 402A and 402B. Switches S1 404A, S2 404B and S3 405allow transmit baseband signals from DAC 402A and DAC 402B to be coupledto low pass filters (LPF) 406A and 406B. Transmit baseband signals fromLPF 406A and 406B are coupled to mixers 410A and 410B. Mixers 410A and410B receive local oscillator signal from local oscillator buffers 412Aand 412B and upconvert transmit baseband signals to radio frequencysignals. Radio frequency signals at output of mixers 410A and 410B arecoupled to driver amplifiers (DA) 426A and 426B. Switches S4 430A, S5428, and S6 430B allow radio frequency transmit signals from DA 426A and426B to be coupled to outputs TX1 and TX2. PLL, VCO, VCO Buffer, andDivider provide quadrature LO signals to local oscillator buffers 412Aand 412B.

It should be understood that switches 404A S1 and 404B S2 can beintegrated within DAC 402A and 402B, for example by providing a “openswitch” mode in the DAC where the DAC output is set to a high impedancestate and no signal is provided from the DAC. When the DAC 402A or 402Boperates normally and outputs a signal, this is equivalent to closingswitch 404A S1 or 404B S2 respectively and allowing signal from DAC 402Aor 402B to be coupled to subsequent stages of transmit system 400.

Likewise, switches S4 430A and S6 430B can be integrated within driveramplifier 426A and 426B respectively, for example by use of a cascodeamplifier within driver amplifier which can be enabled or disabled.Within DA 426A enabling the cascode amplifier is equivalent to closingswitch S4 430A and disabling the cascode amplifier is equivalent toopening switch S4 430A. Within DA 426B enabling the cascode amplifier isequivalent to closing switch S6 430B and disabling the cascode amplifieris equivalent to opening switch S6 430B.

FIG. 5 illustrates an architecture of a transmit diversity architecturewhen configured for legacy operation. FIG. 5 illustrates the system 500in one possible configuration for legacy operation. Switches 504A S1 and505 S3 are closed while switch 504B S2 is open, allowing signal DATA1 todrive DAC 502A. DAC 502B is not used in the configuration and can bedisabled to save power. DAC 502A transmit baseband signal is coupled toLPF 506A and LPF 506B. LPF outputs are coupled to mixers 510A and 510B.Mixer outputs are coupled to driver amplifiers 526A and 526B. Switches530A S4 and 528 S5 are closed while switch 530B S6 is open providingtotal power of radio frequency transmit signal to signal TX1. Otherconfigurations for legacy mode are possible, as when input data isprovided on DATA1 and output signal is on TX2, input data is on DATA2and output signal is on TX1 and input data is on DATA2 and output signalis on TX2. As will be described later this document, the location of 505S3 can also be varied.

FIG. 6 illustrates an architecture of a transmit diversity architecturewhen configured for MIMO or transmit diversity operation. FIG. 6illustrates the system 600 in one possible configuration for MIMOoperation. In MIMO operation different input signals are provided onDATA1 and DATA2 as previously described in FIG. 3. Switches 604A S1 and604B S2 are closed while switch 605 S3 is open. Transmit baseband signalfrom DAC 602A is coupled to LPF 606A. A different transmit basebandsignal from DAC 602B is coupled to LPF 606B. Transmit baseband signaloutput from LPF 606A is coupled to mixer 610A. A different transmitbaseband signal from LPF 606B is coupled to mixer 610B. Radio frequencytransmit signal from mixer 610A is coupled to driver amplifier 626A. Adifferent radio frequency transmit signal from mixer 610B is coupled todriver amplifier 626B. Switches 630A S4 and 630B S6 are closed whileswitch 628 S5 is open, allowing transmit signal that originated withDATA1 stream to be coupled to output TX1 and a different transmit signalthat originated with DATA2 stream to be coupled to output TX2.

FIG. 7 illustrates an embodiment of a system architecture of a transmitdiversity architecture with optimized power consumption and an area forUMTS and LTE systems with two transmit chains and the entirearchitecture divided into two pieces. In FIG. 7, in the system 700, Data1 is input through a digital to analog converter (DAC) 702A and Data 2is input through (DAC) 702B. Data 1 and Data 2 are linked by switch 701.After DAC 702A, the Data 1 passed through switch 704A, while Data 2passes through switch 704B. These two paths are connected through switch705. Data 1 then passes through low pass filters 706A-C, while Data 2passes through 706D-F. After the low pass filters 706A-F, the paths arelinked through switch 708. Data 1 then passes through mixers 710A-C, andData 2 passes through mixers 710D-F. The paths are connected throughbuffers 712A and 712B. Divider 714 provides an input between buffers712A and 712B. The divider 714 input originates with a crystaloscillator 722 that provides input to PLL 720. The PLL input is providedto variable oscillator 718. The VCO 718 output is sent to the VCO buffer716 that in turn provides input to the divider 714.

The output from the mixers 710A-F is connected through switch 724. Theoutput from the mixers 710A-F are then passed through amplifiers 726A-Cfor Data 1 and 726D-F for Data 2. The output between Data 1's path andData 2's path is connected by switch 728. Each transmit path, Tx1 andTx2 is connected to a switch, for Tx1 switch 730A and for Tx2 switch730B and switch 728. This produces a longer path for Data 2 to traverse,which may not be desirable in some systems. In tracing the paths afterthe signals exit switches 704A and 704B it is apparent that Data 1 takesa straight path through switch 730A, while Data 2 must pass throughswitch 730A and switch 728.

The architecture in FIG. 7 provides for maximum power to be delivered atoutput Tx1. This is achieved by closing switch 704A, switch 705, 730A,and switch 728. Total power may also be achieved at Tx2 by adjusting theswitch settings, closing switches 704A, 705, 708, and 730B. Thearchitecture of FIG. 7 also allows for power consumption control byselecting how many low pass filters 706A-F are enabled for a givenoutput signal strength at TX1 or TX2. Power consumption control may alsobe exercised by selecting how many mixers 710A-F are enabled for a givenoutput signal strength at TX1 or TX2. Power consumption control may alsobe exercised by selecting how many driver amplifiers 726A-F are enabledfor a given output signal strength at TX1 or TX2. In the upper signalpath LPF 706A-C may have relative sizes of 1×, 2×, or 4× or anycombination thereof. Mixer 710A-C may have relative sizes of 1×, 2× or4× or any combination thereof. Driver amplifier 726A-C may have relativesizes of 1×, 2× or 4× or any combination thereof. Power consumptionscaling and gain scaling by ratios of 1×, 2× and 4× is an exampleembodiment and other scaling ratios may be used.

FIG. 8 illustrates a second embodiment of a transmit architecture foruplink MIMO and transmit diversity. Two DACs, 802A and 802B are providedalong with a crossed switch pathway with switches 830A, 830D, 830C, and830B. After exiting the DACs 802A and 802B, Data 1 is passed throughswitch 804A, while Data 2 passes through 804B. The paths are connectedto switch 805. Data 1 then passes through low pass filters 806A-C andData 2 passes through low pass filters 806D-F. The paths are thenconnected through switch 808. The embodiment of FIG. 8 provides equallength paths because of the cross switch. Data 1 then passes throughmixers 810A-C, and Data 2 passes through mixers 810D-F. The paths areconnected through buffers 812A and 812B. Divider 814 provides an inputbetween buffers 812A and 812B. The divider 814 input originates with acrystal oscillator 822 that provides input to PLL 820. The PLL input isprovided to variable oscillator 818. The VCO 818 output is sent to theVCO buffer 816 that in turn provides input to the divider 814.

The output from the mixers 810A-F is connected through switch 824. Themixers 810A-F are then passed through amplifiers 826A-C for Data 1 and826D-F for Data 2. Data 1 and Data 2 then passes through the crossedswitches as described above.

In diversity mode operation, switches 804A and 830A are closed in theupper transmit chain and 804B and 830B are closed in the lower transmitchain. When operated in this configuration, half of the power is outputat Tx1 and half at Tx2 for a balanced mode that avoids mixing products.

FIG. 9 illustrates a third embodiment of a transmit architecture foruplink MIMO and transmit diversity. Two DACs, 902A and 902B are providedalong with a crossed switch pathway with switches 930A, 930D, 930C, and930B. After exiting the DACs 902A and 902B, Data 1 passed through switch904A, while Data 2 passes through 904B. The paths are connected toswitch 905. Data 1 then passes through low pass filters 906A-C and Data2 passes through low pass filters 906D-F. The paths are then connectedthrough switch 908. Data 1 then passes through mixers 910A-C, and Data 2passes through mixers 910D-F. The paths are connected through buffers912A and 912B. Divider 914 provides an input between buffers 912A and912B. The divider 914 input originates with a crystal oscillator 922that provides input to PLL 920. The PLL input is provided to variableoscillator 918. The VCO 918 output is sent to the VCO buffer 916 that inturn provides input to the divider 914.

The output from the mixers 910A-F is connected through switch 924. Themixers 910A-F are then passed through amplifiers 926A-C for Data 1 and926D-F for Data 2. In this embodiment a switch is provided before poweramplifier assembly 928. A switch 932A is provided before power amplifier934A for Data 1. A switch 932B is provided before power amplifier 934B.The paths are connected by switch 930. This third embodiment provides anequal signal path.

FIG. 10 illustrates a third embodiment of a transmit architecture foruplink MIMO and transmit diversity. Two DACs, 1002A and 1002B areprovided along with a crossed switch pathway with switches 1030A, 1030D,1030C, and 1030B. After exiting the DACs 1002A and 1002B, Data 1 passedthrough switch 1004A, while Data 2 passes through 1004B. The paths areconnected to switch 1005. Data 1 then passes through low pass filters1006A-C and Data 2 passes through low pass filters 1006D-F. The pathsare then connected through switch 1008. Data 1 then passes throughmixers 1010A-C, and Data 2 passes through mixers 1010D-F. The paths areconnected through buffers 1012A and 1012B. Divider 1014 provides aninput between buffers 1012A and 1012B. The divider 1014 input originateswith a crystal oscillator 1022 that provides input to PLL 1020. The PLLinput is provided to variable oscillator 1018. The VCO 1018 output issent to the VCO buffer 116 that in turn provides input to the divider71014.

The output from the mixers 1010A-F is connected through switch 1024. Themixers 1010A-F are then passed through amplifiers 1026A-C for Data 1 and1026D-F for Data 2. In this embodiment a switch is provided before poweramplifier assembly 1028. A switch 1032A is provided before poweramplifier 1034A for Data 1. A switch 1032B is provided before poweramplifier 1034B. A cross switch consisting of switches 1030A and 1030Bis provided. This embodiment a crossed switch is provided just beforethe power amplifiers 1034A and 1035B. The embodiment illustrated in FIG.10 provides for mutually exclusive transmission paths.

In each of the embodiments depicted in FIGS. 4-10, the transmit branchesTx 1 and Tx 2 are half-sized. The signal between Paths 1 and 2 may bere-combined using switch 705, 805, 905, or 1005 (at the low pass filterinput), 708, 808, 908, and 1008 (at mixer input), 724, 824, 924, and1024 at (DA input), 701, 801, 901, and 1001 (at DAC input). Thisprovides for maximum flexibility. While multiple switches areillustrated and may be incorporated, at a minimum only one switch needsto be implemented, one of 705, 805, 905, and 1005, 708, 808, 908, and1008, or 701, 801, 901, and 1001 rather than 724, 824, 924, and 1024 maybe selected. While the embodiment of FIG. 8 provides an extra switch,the architecture provides more balancing between the two transmitstreams. Both signal paths traverse one switch at the DA output, whichprovides support for legacy modes and devices.

FIGS. 4, 5, 6, 7 and 8 depict combining the signals inside thetransceiver, while FIGS. 9 and 10 make the signal combination inside thepower amplifier.

FIG. 11 provides a flow chart of a method of wireless communicationusing an apparatus providing transmit diversity with optimized powerconsumption. In step 102 the transmit path is selected and a firstswitch after a digital to analog converter is closed. In step 80411, asecond switch is closed between the two transmit paths. The signal isthen processed through the low-pass filter in step 1106. After thelow-pass filter processing is complete, the signal is then processedthrough at least one mixer in the transmit path in step 1108. The signalis then processed through at least one driver amplifier in each transmitpath in step 1110. After the driver amplifier amplifies the signal, athird switch is closed in step 1112 and the signal is ready to betransmitted.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. The accompanyingmethod claims present elements of the various steps in a sample order,and are not meant to be limited to the specific order or hierarchypresented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed as a means plus functionunless the element is expressly recited using the phrase “means for.”

What is claimed is:
 1. An apparatus for transmit diversity in a multipleinput multiple output (MIMO) network, comprising: two input digital toanalog converters, each accepting a data input; two transmit paths, eachpath comprising at least one low pass filter, at least one mixer, and atleast one driver amplifier; a first switch connecting the two transmitpaths before the driver amplifier; and a second switch connecting thetwo transmit after the driver amplifier.
 2. The apparatus of claim 1,further comprising a cross-switch composed of two switches installed inthe transmit path of both transmit signals following the at least onedriver amplifier and before a power amplifier in each transmit path. 3.The apparatus of claim 1, further comprising a cross-switch composed oftwo switches installed in the transmit path of both transmit signalfollowing the at least one driver amplifier.
 4. The apparatus of claim1, further comprising a switch between the two transmit paths before apower amplifier in each transmit path and before a switch before thepower amplifier in each transmit path.
 5. The apparatus of claim 1,wherein the first switch connects the two transmit paths before the twodigital to analog converters.
 6. The apparatus of claim 1, wherein thefirst switch connects the two transmit paths after the two digital toanalog converters and before the at least one low pass filter.
 7. Theapparatus of claim 1, wherein the first switch connects the two transmitpaths after the at least one low pass filter and before the at least onemixer.
 8. The apparatus of claim 1, wherein the first switch connectsthe two transmit paths after the at least one mixer and before the atleast one driver amplifier.
 9. The apparatus of any preceding claimwhere gain control and power consumption control can be implemented byselecting among multiple sizes for the at least one low pass filter, orat least one mixer or at least one driver amplifier.
 10. A method forproviding total power from one transmit path, comprising: selecting atransmit path and closing a first switch after a digital to analogconverter; closing a second switch between the two transmit paths toprovide for use of at least one low pass filter or mixer or driveramplifier in each transmit path; processing a signal through the atleast one low pass filter or mixer or driver amplifier in each transmitpath, wherein half of a total power is allocated to each transmissionpath; and closing a third switch after the at least one driver amplifierin each transmit path to force the half-power from one transmit pathinto one output.
 11. The method of claim 10, wherein the third switch isa cross-switch between both transmit paths and one branch is closed. 12.An apparatus for providing total power from one transmit path,comprising: means for selecting a transmit path and closing a firstswitch after a digital to analog converter; means for closing a secondswitch between the two transmit paths to provide for use of at least onelow pass filter or mixer or driver amplifier in each transmit path,wherein half of the total power is allocated to each transmission path;and means for closing a third switch after the at least one poweramplifier in each transmit path to force the half-power from onetransmit path into one output.
 13. The apparatus of claim 12, whereinthe third switch is a cross-switch installed in the transmit path ofboth transmission paths.
 14. A non-transitory computer-readable mediumhaving instructions stored thereon, which when executed by a processor,causes the following to occur: selecting a transmit path and closing afirst switch after a digital to analog converter; closing a secondswitch between the between the two transmit paths to provide for use ofat least one low pass filter in each transmit path; processing thesignal through the at least one low pass filter in each transmit path;processing the signal through the at least one mixer in each transmitpath; processing the signal through the at least one power amplifier ineach transmit path, wherein half of a total power is allocated to eachtransmission path; and closing a third switch after the at least onepower amplifier in each transmit path to force the half-power from onetransmit path into one output.
 15. The non-transitory computer readablemedium of claim 9, further comprising instructions for closing onebranch of a cross switch that is the third switch.